Mammoth Lakes-Yosemite

The non-instrument-rated pilot departed on a cross-country flight. Radar track data revealed the airplane traveled on a relatively straight course to the northeast for about 32 minutes. Near the end of the flight track data, the track showed an increasingly tight left spiraling turn near the accident site. The airplane impacted steep sloping terrain, and a postimpact fire ensued. As a result of the impact, the airplane was segmented into several sections. Examination of the wreckage revealed no evidence of mechanical malfunction or failures that would have precluded normal operation. The attitude indicator instrument was disassembled, and the vacuum-powered rotor and housing revealed rotational scoring damage, indicating the instrument vacuum system was operational at the time of the accident. The investigation found no evidence indicating the pilot checked the weather or received weather information before departure. The surrounding weather reporting stations near the accident site reported wind conditions with peak gusts up to 47 knots around the time of the accident. The pilot likely encountered mountain wave activity with severe turbulence, which resulted in loss of control of the airplane and impact with terrain. Contributing to the accident was the pilot’s failure to obtain a preflight weather briefing, which would have alerted him to the presence of hazardous strong winds and turbulent conditions. Postmortem toxicology testing of the pilot’s lung and muscle tissue samples detected several substances that are mentally and physically impairing individually and even more so in combination for performing hazardous and complex tasks. However, blood concentrations are needed to determine the level of impairment, and no blood samples for the pilot were available. While the pilot was taking potentially impairing medications and likely had conditions that would influence decision making and reduce performance, without blood concentrations, it was not possible to determine whether the potentially impairing combination of medications degraded his ability to safely operate the airplane.

According to the pilot, he checked the winds via his onboard weather reporting device during the run-up, and he stated that the 25 knot wind sock was about ¾ full just moments before the takeoff roll. He reported that during the takeoff roll the airplane encountered a significant wind gust from the right. He stated that the wind gust forced the airplane to exit the left side of the runway, the landing gear collapsed, and the airplane collided with metal pylons which surrounded the wind sock. The airplane sustained substantial damage to both wings, fuselage, horizontal stabilizer and elevator. The pilot reported that there were no mechanical failures or anomalies prior to or during the flight that would have prevented normal flight operation. According to the Airport/Facility Directory, the Airport Remarks state: Airport located in mountainous terrain with occasional strong winds and turbulence. Lighted windsock available at runway ends and centerfield. With southerly crosswinds in excess of 15 knots, experiencing turbulence and possible windshear along first 3000´ of Runway 27. The reported wind at the airport during the time of the accident was from 200 degrees true at 22 knots, with gusts at 33 knots, and the departure runway heading was 27. According to the pilot operating hand book the maximum demonstrated crosswind component for this airplane is 17 knots. The crosswind component during the time of the accident was 26 knots.

Due to the impending arrival of a snow storm, the certificated commercial pilot and 5 passengers departed one day earlier than planned, from an uncontrolled airport located in mountainous terrain to begin a night, cross country flight. Instrument meteorological conditions prevailed. Prior to departure, the pilot was given an ifr clearance void time from an ARTCC. The pilot was climbing toward a VOR located about 27 miles southeast of the departure airport while attempting to contact the ARTCC to open his instrument flight plan. The pilot failed to maintain terrain clearance, and became lost/disoriented. The airplane struck trees and snow covered terrain at 10,200 feet msl, 7 nautical miles and about 22° to the right of the intended course. Four passengers were killed while two other occupants, among them the pilot, were injured.

The aircraft took off from an airport whose runways had been closed for snow removal. A notam had been filed with the Fresno FSS by the Mammoth Lakes Airport Manager at 0900 hours for taxi and runway snow removal. The pilot was aware of the notam because the manager and a lineman both said they advised him of it. Several witnesses saw the pilot enter the aircraft after declining engine pre-heat or aircraft de-icing. When advised by the lineman that the 2 qts of oil that the pilot requested did not 'register on the dipstick.' The pilot ordered another qt to be 'thrown' in and 'hurry up.' No preflight or warm up or before takeoff check was noted by observers. Turning immediately onto the runway and rolling for takeoff the pilot passed a snow plow. The aircraft used 7,000 feet (all of the runway) and left the ground in a nose high attitude. The airport elevation is 7,128 feet msl. The aircraft first struck a dirt mound 3/4 of a mile after takeoff. After maintaining further flight for approximately 280 feet which crossed a small ravine the aircraft collided with the far side of the ravine and started to break apart, stopping 144 feet further east. The pilot, sole on board, was killed.

Shortly after liftoff from Mammoth Lakes-Yosemite Airport, while in initial climb, both propellers oversped. As the airspeed was insufficient, the aircraft stalled and crashed in flames near the airport. The aircraft was totally destroyed and all five occupants were killed.